The system of the IEEE 802.16e that is undergoing international standardization with respect to broadband wireless access systems, does not have a layered architecture comprised of a HLR (Home Location Register), a VLR (Visitor Location Register), a MSC (Mobile Switching Center), a BSC (Base Station Controller), a RNC (Radio Network Controller), and the like, as in the existing 2G and 3G mobile communication systems, but instead, is comprised of only a MSS (Mobile Subscriber Station), a BS (Base Station) and a ASA (Authentication Service Authorization).
The broadband wireless access system defines the protocols of the MAC (Medium Access Control) layer and the PHY (PHYsical) layer that are common between the base station and the mobile station (MSS). FIG. 1 depicts an exemplary protocol layer architecture for a broadband wireless access system.
FIG. 2 depicts the procedures for searching and broadcasting neighbor base station information in a broadband wireless access system according to the related art.
If the mobile station (MSS) receives a neighbor base station information broadcast message (MOB_NBR-ADV) from a serving base station [S21], the mobile station temporarily stops data reception from the serving base station and transmits a scan request message (MOB_SCN-REQ) in order to obtain a certain amount of time (duration=N frames) for performing channel quality measurements of neighbor base stations [S22]. While the mobile station measures the channel quality of neighbor base stations, the serving base station stops any data transmission to the mobile station, but stores such data that be may be transmitted after the scanning (searching) duration requested by the mobile station has been completed. The MOB_NBR-ADV is a message that is broadcast by the serving base station to the mobile station in order to provide information related to neighbor base stations, and may contain the total number of neighbor base stations, identifiers for the neighbor base stations, frequencies used by the neighbor base stations, channel information of the neighbor base stations, and the like.
In response to the scan request message (MOB_SCN-REQ) sent from the mobile station, the serving base station transmits a scan response message (MOB_SCN-RSP) [S23]. In FIG. 2, the serving base station is guaranteed a time duration from the Mth frame until the Nth frame to perform channel quality measurements for the neighbor base stations. In other words, the scanning (searching) duration requested by the mobile station is guaranteed by the scan request message and the scan response message between the mobile station and the serving base station, and the mobile station and serving base station agree that the guaranteed duration should begin after the Mth frame. The mobile station then measures the channel quality of neighbor base stations during the guaranteed scanning duration [S24, S25]. The mobile station provides the scanning results to the serving base station by transmitting a scanning result report message (MOB_SCAN-REPORT) [S26].
As explained above, in the related art, the messages used by the mobile station to perform scanning that are transmitted and received with the base station are defined, but the operations actually related to scanning are not defined for the protocol stack (layers) within the mobile station and the protocol stack (layers) within the base station. Namely, there are no definitions for the primitives with respect to information transferred between the MAC layer and upper management entity via the NCMS (Network Control Management System), within the protocol stacks of the mobile station and the base station, respectively.